G4 MDD - CPU upgrade question

[commodorejohn]

Okay, I've just acquired a 2002 MDD Power Mac (1.25GHz DP) and gotten it up and running. It's quite a nice machine, but I've noticed that it's running a bit hot, even though the fans are working fine. Since the CPU is swappable, and since it's primarily an OS9 box and thus the dual-processor setup isn't that much of an advantage, I've been wondering if it might not be better to swap the CPU daughterboard out for a single-processor one, to cut down on the heat. I'm just wondering, if I could locate a 1.42-2GHz single-CPU module, is that still going to be a lower heat output than a single 1.25GHz CPU? I'd assume so, but I've never done anything with serious Mac upgrading before.

Anyway, would anybody be interested in swapping a 1.25GHz+ single-CPU board for my dual-1.25GHz board? I'm sure someone here could probably make better use of it.

[Bunsen]

When you say it's running a "bit hot", is that as indicated by the CPU temperature sensor, or by feeling the heat output with your hand? If it's the former, what temperature is indicated? As these machines are fairly old now, it may be that the thermal paste between CPU and heatsink has dried out and needs renewing.

It's probably also worth cleaning out any dust bunnies that may have taken up residence.

I would assume (not that I know) that your surmise about a single processor running cooler is correct, and it would be true that a faster single CPU is better for OS 9: if you decide to go ahead with a swap, it's probably best to make a listing in the Trading Post. NB; the fastest CPUs (like the 2GHz part you mentioned) are third party upgrades from the likes of Sonnet, not OEM Apple parts.

[Byrd]

When you say running hot - how hot? If it's not crashing, it's fine. I'd more look into replacing the fans in your MDD with quieter, more efficient units than pulling the CPU for a single, which will severely hamper OS X performance when you run it. Also look into replacing the thermal grease on the CPU, and graphics card heatsink.

[commodorejohn]

Good point about the thermal paste, I'll freshen that up when I get a chance. Temperature Monitor shows the board temperature at 136F with nothing open but the Finder and Temperature Monitor; I'm no expert on this stuff, but that seems a little high to me. When I had it unpacking a large archive with StuffIt this morning, it actually went into suspend due to heat and I had to let it cool off for half an hour before it would finish

I'd more look into replacing the fans in your MDD with quieter, more efficient units than pulling the CPU for a single, which will severely hamper OS X performance when you run it. Also look into replacing the thermal grease on the CPU, and graphics card heatsink.

I'm not really concerned about OSX performance; as I said, this is primarily an OS9 machine. I would be interested in replacing the fans, though - at least the big one, which is a bit rattly anyway. Any idea where I can get a replacement? Also, the heatsink is an aluminum one, and I'm told there was a copper version on some of the faster machines; is there a place I can get one of those?

[Byrd]

Thermal shutdown is not normal and suggest either dried up thermal grease, dust bunnies, or the heatsink isn't seated properly on the CPU. Check out your local online PC store for replacement fans.

I'd keep the dual 1.25, and buy a single 1.25 (looks like you might be lucky seeing your WTB). I fixed up a single 1Ghz MDD for a friend recently, and it really was a lot slower than I'd expected running 10.5 (2GB RAM, Geforce 6800 PC flashed graphics card, fast 7200RPM HD). Noting you can get dual 1.42s off eBay very cheaply, I suggested my friend spend $30 - 50 on one of these should he find it getting painfully slow for day-to-day tasks.

JB

[commodorejohn]

Hmm, well, I've got a 1.25GHz single CPU lined up in exchange for some other stuff, so I'll still have the 1.25GHz DP card if it does turn out to be too slow. But as I said, my concern is much more for thermal issues and OS9 performance than OSX performance, so I don't expect it'll be an issue.

I'll take a look around at fan options, in any case - I wouldn'tve expected this would be something you could buy from a PC parts retailer, I'dve thought it would be some proprietary form factor or something

[BGoins12]

I replaced the 3 blade fan in my MDD with a better 7? blade fan. It stays WAY cooler. It runs at 45-47*C now. It used to run at 59-60 with the old, loud fan.

[theos911]

I definitely suggest checking and replacing your cpu goo.

[commodorejohn]

Yikes. The thermal paste was so old and crappy it came off in chunks. Didn't even leave a smear behind. I replaced it, and now it idles at around 101F; even a short gaming session only pushed it to 111. Quite an improvement! I still think I'll give the single-CPU approach a try, but it's nice to know that the normal temperature for the DP card is a lot more reasonable than 136F!

[commodorejohn]

Coming back to this, I'm just curious if anybody has any idea how much of a performance impact the presence of L3 cache has on a G4. I ask because I was reading about upgrade options for the MDD Macs, and it seems that of the three third-party accelerators listed there, only the slowest (dual 1.33GHz) has an L3 cache. I've heard some anecdotal evidence that it can make a noticeable difference, and given that the main bottleneck on fast G4s is the FSB (167MHz and no DDR support, IIRC,) I'd imagine that it does, but I'm just curious if anybody's made thorough measurements. If it is a real performance impact, I'd kind of suspect that swapping in the dual 1.42GHz CPU card (with L3 cache) from a FW800 MDD would be the best option all-around, not just for OSX...

[johnklos]

It all depends on what you're running. OS X would make heavier use of L3 caches because much of the code is larger. OS 9 typically is fine with the 512k of CPU speed L2 cache on the 7447a cards. Of course, if you can get 7448 cards with 1 meg of L2 at CPU speed, that'd easily be much faster than the 256k of CPU speed L2 and 1 or 2 megs of 200 - 250 MHz L3.

I have a 1.733 GHz 7448 on an older 133 MHz SDRAM bus which is noticeably faster than a 1.8 GHz 7447a on a 333 MHz DDR bus.

[Unknown_K]

Anybody have a link for the less noisy fan replacements? For some reason I bid on a MDD 867 Mhz and won it (they only made 867 duals correct?).

[trag]

Anybody have a link for the less noisy fan replacements? For some reason I bid on a MDD 867 Mhz and won it (they only made 867 duals correct?).

Well, if you don't get specific recommendations, I'd identify the type of fans in each position (2 X 60mm X 25mm in power supply, 120mm X 25mm opposite CPU, mumble X 25mm under optical drive?) and then look for well regarded quiet alternatives.

IIRC, this site has good reviews on fans: http://www.silentpcreview.com/articleindex

But don't get too compulsive (unless you enjoy that sort of thing) because the pursuit of the silent PC can drive a man mad....

[Unknown_K]

Not too worried about a silent PC, but the seller said the machine was noisy so the fans might just need lubed, replaced, or he isn't used to a windtunnel mac.

I assume the fans might be controlled by a sensor monitoring CPU temp and the CPU heatsink might be clogged with dust or they used too much heatsink compound on the CPU and it has dried up causing them to overheat. Will find out when UPS gets here, I strip my machines when I get them anyway to clan them and look around so I will see whats up.

I will probably just keep my 1.25Ghz QS in my room, that machine is quiet enough to leave running.

[commodorejohn]

Replacing the thermal glue did result in a definite improvement in fan noise with the MDD in the original post, definitely give that a try.

[theos911]

But don't get too compulsive (unless you enjoy that sort of thing) because the pursuit of the silent PC can drive a man mad....

My room has 5 aquariums and probably a dozen various airpumps humming away all the time! My PC's fans need to be on medium before I even notice they are on. (But, it is an old P4 running Ubuntu, so I feel the heat in the form of slowdown before I ever hear the fans.)

[Unknown_K]

My main machine for everyday use is a Dell Dimension 8300 P4 3Ghz HT, that machines fan likes to rev up sometimes when the CPU is very busy. Most of my machines are pretty quiet actually, the Athlon 64 machines I own are probably the quietest.

[Unknown_K]

Well it is here and running (put a 160GB HD from my spare QS into it). I didn't check how loud it was before I stripped it and cleaned it, but it isn't that loud now. I did remove the heatsink and clean off the old heatsink compound (greyish no idea if it was original). Not too bad of a machine actually.

[commodorejohn]

Less pleasant to work inside than the other Blue-and-White-model tower cases, but yeah, overall a pretty good machine. I'm a little surprised at how well later G4 machines stack up, performance-wise - the 1.67GHz PowerBook I had for a while bested my similarly-clocked Asus Eee in basically everything that wasn't disk- or memory-bound.